Preparation of acyloins



Patented Apr. 2, 1935 UNITED STA OFFICE to The E. I. du Pont de Nemours & Company, Incorporated, WilmingtomDeL, a corporation of Delaware No Drawing.

Application August so, 1933, Serial No. 687,485

15 Claims. (crest-134) This invention relates to improvements in the preparation of acyloins by the reaction of an al kali metal with esters of fatty acids. More particularly, this invention relates to the prepara- 5 tion of acyloins of higher molecular weight, by

(1) 201130 O CHa+4Na)2NaO CHg-l-CHaC-ONQ CH;OONa

(2) CHaCONa+2HgO CHaC-OH-l-ZNaOH a CH; ONa OH: OH

H mire-0H by rearrangement 0-011 CH3C-OH GE s-0 0 Liquid isomers, some intermediate products and some by-products of the main reaction also are found in the final solution. The work of Bouveault and Locquin Bull. Soc. Chim. (3) 35 629 (1906) showed that this reaction was applicable to esters of acetic, propionic and butyric acids. Recently Corson, Benson & Goodwin (J. A. C. S. 52 3988 (1930)) have attempted to extend this reaction to esters of acids with higher molecular weight. They prepared acyloins from esters of acids containing 6 carbon atoms, but reported that with laurate or myristate esters the reaction was so extremely slow and incomplete that no attempt was made to work up the product. Their experiments with these esters involved the use of ethyl ether as a solvent at its boiling point. I have now discovered, that contrary to what could have been predicted on the basis of information previously available, esters of higher fatty acids such as those occurring as glycerides in cocoanut oil, palm oil and similar materials can readily be made to react with alkali metals to give acyloins in very good yield.

The objects of this invention are to provide means of effecting a rapid reaction of sodium or other alkali metal with esters of the higher fatty acids containing 12 or more carbon atoms; to provide means of isolating in pure form from such reaction mixtures good yields of acyloins; and to provide a satisfactory method of isolating in pure form the acyloins from any solvent such as the ethyl ether previously described; further objects will appear from the description of the invention.

I have discovered that the failure to secure acyloins from the esters of the acids containing 12 or more carbon atoms was due to the fact that the sodium derivatives of the reaction products or byproducts were insoluble in the ethyl ether solvent used. These insoluble materials so encrust the sodium that reaction practically stops as soon as it has started to any degree. I have now discovered that if the reactions with the esters of the higher acids be run with the sodium at a temperature above its melting point, agitation of the liquid will cause a sufficient disintegration of the encrusted globules as to continually present fresh surfaces of sodium to the reaction and thus permit the reaction to proceed to completion and the formation of the acyloins.

Corson et a1, supra, described having attempted to prepare butyroin in boiling toluene. Unsatisfactory results were secured apparently, principally because of fires occurring when it was attempted to recover the reaction product. It is .not indicated whether or not butyroin was actually produced. In my studies of the reactions involved in the formation of butyroin and the similar acyloins derived-from the esters of the lower fatty acids, I have found that the high temperatures, i. e., those above the melting point of sodium are unfavorable to the reaction and lesser yields are obtained than in ethyl ether. In the case of these lower members of the'series the solubility of the acyloins in ethyl ether is sufficient to prevent the disturbing encrustation by the intermediate reaction products, alcoholate's or the like so that the reaction can proceed to the desired final product without difficulty.

Therefore, in effecting the reaction of sodium with the esters of the higher fatty acids, I have discovered it is desirable to employ a moderately high boiling hydrocarbon or ether as a medium for dispersing the sodium and a diluent solvent for the ester. The choice of a particular'solvent will depend to some extent on the nature of the ester being used; For convenience it is preferable to use a liquid such as toluene or xylene with a boiling point sufficiently near or above the melting point of sodium, so that a temperature of 100-110" C. can be maintained at ordinary pressure without undue loss of solvent. I have prepared acyloins with equal success from the methyl, ethyl and butyl esters of the higher fatty acids; I have also made mixtures of acyloins from glycerides and mixed glycerides such as cocoanut oil and hydrogenated cottonseed oil. I have used esters of saturated fatty acids with 12 to 18 carbon atoms and find the same situation as to solvent.

I have further discovered that in carrying out these reactions it is advisable as above stated, to have an inert solvent having a boiling point sufficiently above the melting point of sodium as to maintain sodium in a molten stage at ordinary pressures for the solvent. Furthermore, I have found it is advantageous to suspend-the sodium by fairly rapid agitation in. one portion of the solvent required and to dissolve the ester in the remaining portion and then slowly add the ester solution to the agitated suspension at -110 C.

I have also found that the method of recovery of the acyloins, whether of the lower or the'higher' members of the series, has a very important bearing on the yields obtained. In the methods described by Corson et al, supra, undoubtedly decomposition cf the sodium ester condensation products occurred to appreciable degrees. The obvious method of obtaining solidmaterials of this nature from ether or similar volatile solvents" is to distil oif the solvent. This I have discovered causes losses which may occur in a variety of ways, particularly due to the heating even at reduced pressures. To insure a good yield I have found it advantageous to decompose first any unchanged sodium with an alcohol, e. g., methanol, then to neutralize the reaction mixture with approximately 1% excess of about 4.5 molar sulfuric acid solution at a temperature of not over 25 C. In carrying outthis decomposition and neutralization, methanol is first added in the amount equivalent to about one-half of the sodium employed. The aqueous acid solution is then slowly added with cooling, preferably maintaining a temperature of between 15-20 C.v The sodium sulfate formed and any excess acid, is then removed from the xylene solution by washing with water. After the xylene solution is concentrated and cooled to 0 C. for about one hour, the acyloin is nearly completely thrown out of solution in crystalline form. Ihave found in general that the acyloins containing 20 or more carbon atoms, 1. e., those prepared from esters of acids containing 10 or more carbon atoms, can be thrown out quantitatively at the first precipitation by only moderate concentration of the solution, e. g., by concentrating the solution to one-third to one-half of its original volume. If the xylene solution is cooled to 20 C. the acyloins can be practically completely precipitated without concentration; with the extreme higher members, less cooling is required. Solution of the acyloins of the lower molecular weight, however, will require further concentration. An isomeric fatty acid condensation product remains in the mother liquor and can be isolated subsequently by distilling off the hydrocarbon solvent.

The invention is illustrated by the following examples:

Example 1 Methyl stearate, 515 gms., in 1.5 liters of xylene was added in the course of 1.5 hours, to a suspension of 80.5 gms. of sodium in another 1.5 liters of xylene which was mildly agitated at C. The agitation was continued for 0.5 hours after the addition of the ester solution was completed. After cooling to 20 C., 50 gms. of methanol was slowly added, followed by a 1% excess of 4.5 molar sulfuric acid with cooling to 15-20 C. The Xylene solution was washed free of acid and salt with water and the acyloin separated by fractional crystallization. The products obtained were 381 gms. of crystalline acyloin (keto-alcohol) melting at 82 C., (a yield of 82.2%) and 66 gms. of liquid isomer (corresponding to 15% yield).

Example 2 Methyl palmitate, 540 gms., in 1.5 liters of xylene was added to a suspension of 92 gms. of sodium in 1.5 liters of xylene at 110 C. as in Example 1. The products were 301 gms. of crystallihe wax-like acyloin (keto-alcohol), melting at 78 C., (62.6% yield) and 83 gms. of liquid isomer, (17.3% yield).

Example 3 Methyl myristate, 666 gms., dissolved in 1.5 liters xylene reacted with gms. of sodium in 1.5 liters of xylene at 105 C. to give 439 gms., (82% yield) of the keto-alcohol, melting at 72 C. and 98 gms. of the liquid isomer, (18.5% yield).

Example 4 Methyl laurate, 551 gms., and 115 gms. of sodi um reacted in xylene as in the above examples yielded 414 gms. (89.9% yield) of the keto-alcohol, melting at 63 C. and 36 gms. (7.8% yield) of the liquid isomer.

Example 5 Example 6 Methyl laurate, 214 gms., was reacted with 46 gms. of finely divided sodium suspended in 1 liter of ethyl ether at 34 C. The keto-alcohol obtained was 20.0 gms. (10.9% yield) and the liquid isomer was 86.4 gms. (47% yield).

Example 7 Methyl laurate, 535 gms., reacted with 115 gms. of sodium in toluene, as in Example 1, gave 418 gms. (91.0% yield) of the keto-alcohol and 217 gms. (4.7% yield) of the liquid'isomer.

Example 8 Ethyl nonylate, 98.5 gms., reacted with 24.4 gms. of sodium in xylene as in Example 1, gave 53.3 gms. 70.8% yield) of the keto-alcohol, melting at 434 C. and 10 gms. (13.3% yield) of the liquid isomer.

Example 9 Butyl caprylate, 500 gms., reacted 115 gms. of sodium in xylene as in Example 1, gave '197 gms. (77.1% yield) of the keto-alcohol, melting at 35 C. and 58.9 gms. (22.9% yield) of the liquid isomer.

Example 10 Methyl caprylate, 40 gms., reacted with 11.7 gms. of sodium, gave 10.7 gms. (41.9% yield) of the keto-alcohol and 14.1 gms. (54.8% yield) of the liquid isomer.

Example 11 Methyl caproate, 40 gms., reacted with 14.3 gms. of sodium in xylene as in Example 1, gave 28.7 gms. of a mixture of the isomeric dimeric condensation products, boiling at 86-96 C. at a pressure of 3 mm. corresponding to a yield of 93%.

Example 12 Mixed methyl esters of lauric and myristic acids in proportions occurring in cocoanut oil (60% of lauric acid and 40% of myristic acid, by weight), 571 grns, reacted with 145 gms. of sodium as in Example i, gave 499.7 gins. (80.8% yield) of the mixed keto-alcohols and 66 gms. (10.7% yield) of a mixture of the liquid isomers.

I claim:

1. Method of preparation of acyloins containing 24 or more carbon atoms which comprises reacting a solution of an ester of a fatty acid containing 12 or more carbon atoms with a molten alkali metal.

2. Method of preparing acyloins containing 24 or more carbon atoms which comprises reacting sodium with an ester of a fatty acid having 12 or more carbon atoms in a solvent at a temperature above the melting point of sodium.

3. Method or preparing acyloins containing 24 or more carbon atoms which comprises reacting sodium at a temperature above its melting point with an ester of a fatty acid having 12 or more carbon atoms in a hydrocarbon solvent, the atmospheric boiling point of which is above the melting point of sodium.

4. Method of preparing acyloins containing 24 or more carbon atoms which comprises reacting sodium at a temperature above its melting point with an ester of a fatty acid having 12 or more carbon atoms in an aromatic hydrocarbon solvent, the atmospheric boiling point of which is above the melting point of sodium.

5. Method of preparing acyloins containing 24 or more carbon atoms which comprises reacting sodium and an ester of a fatty acid containing 12 or more carbon atoms in xylene at a temperature above the melting point of sodium.

6. Method of preparing acyloins containing 24 or more carbon atoms which comprises reacting sodium and an ester of a fatty acid containing 12 or more carbon atoms in toluene at a temperature above the melting point of sodium.

7. Method of preparing acyloins containing 24 or more carbon atoms which comprises reacting sodium with a glyceride of a fatty acid having 12 or more carbon atoms in a solvent at a temperature above the melting point of sodium.

8. Method of preparing acyloins containing 24 or more carbon atoms which comprises adding a solution of an ester of a fatty acid having 12 or more carbon atoms to a suspension of an alkali metal in an inert solvent with agitation at a temperature above the melting point of said metal.

9. Method ofpreparing acyloins containing 24 or more carbon atoms which comprises dissolving an ester of a fatty acid having 12 or more carbon atoms in a hydrocarbon solvent the atmospheric boiling point of which is above the melting point of sodium and adding the solution to a suspension of sodium in a liquid hydrocarbon at a temperature above the melting point of the sodium.

10. In the preparation of acyloins which may be precipitated from the solvent wherein they are dissolved by the reaction of an alkali metal on an ester in a solvent. the method of recovering the acyloin formed which comprises reacting the unchanged alkali metal with an alcohol, neutralizing the resultant solution, washing with water and finally precipitating the acyloin.

11. In the preparation of acyloins which may be precipitated from the solvent wherein they are dissolved by the reaction of sodium on an ester in a solvent, the method of recovering the acyloin formed which comprises reacting the unchanged sodium with an alcohol, acidifying the resultant solution, washing with water and finally precipitating the acyloin.

12. In the preparation of acyloins which may be precipitated from the solvent wherein they are dissolved by the reaction of sodium on an ester in a solvent, the method of recovering the acyloin formed which comprises reacting the unchanged sodium with an alcohol, neutralizing the resultant solution, washing with water, and finally separating acyloin from said solution by fractional crystallization.

13. In the preparation of acyloins which may be precipitated from the solvent wherein they are dissolved by the reaction of an alkali metal on a fatty acid ester in a solvent, the method of recovering the acyloin formed which comprises reacting the unchanged alkali metal with an alcohol, neutralizing the resultant solution, washing with water, concentrating the solution and finally precipitating the acyloin. 1

14. In the preparation of acyloins which may be precipitated from the solvent wherein they are dissolved by the reaction of sodium on a fatty acid ester in a solvent, the method of recovering the acyloin formed which comprises reacting the unchanged sodium with an alcohol, neutralizing the resultant solution, washing with water and finally cooling the solution to precip itate the acyloin.

15. In the preparation of acyloins which may be precipitated from the solvent wherein they are dissolved by the reaction of sodium on a fatty acid ester in a solvent, the method of recovering the acyloin formed which comprises reacting the unchanged sodium with an alcohol, neutralizing the resultant solution, washing with water, concentrating the solution and finally cooling the solution to precipitate the acyloin.

VIRGIL L. HANSLEY. 

